1. Field
One embodiment of the present invention relates to improvements in server apparatus in visual communication systems in which, for example, the server apparatus are connected to telephone exchange apparatuses via communication paths to allow video signals, computer data, and the like to be handled in addition to sound signals.
2. Description of the Related Art
Local network systems are used in offices and business establishments. The local network system accommodates telephone sets as extension terminals in a telephone exchange apparatus such as a private branch exchange (PBX) or a key telephone apparatus. The extension terminals are exchangeably connected to an external communication network such as a public network and extension terminals are exchangeably connected together, by the telephone exchange apparatus to enable calls.
Video conference systems have been proposed which connect a server to which data terminals such as personal computers are connected, to a telephone exchange apparatus via transmission paths.
For the video conference system, a technique has also been proposed by which a telephone exchange apparatus performs control on the basis of a control table containing integrated call connection information on immediate call connections and reserved call connections between terminals involved in the conference to controllably connect target terminals (for example, Jpn. Pat. Appln. KOKAI Publication No. H5-236132).
However, this system is not applicable to VCSs (Visual Communication Systems) in which data communication connections among data terminals are linked to the call statuses of telephone terminals.
Further, to realize VCS, the following measures need to be considered.
To allow a VCS server to correctly perform video communication control on data terminals when, for example, a two-party call is to be made such that visual clients associated with extension terminals involved in the two-party call make video communications with each other, the visual clients must perform a log-on operation on the VCS server before they can make a call (listener registration).
That is, it is assumed that a two-party call is started with one of the visual clients associated with the extension terminals for the two-party call, in a log-on status and the other in a log-off status. Then, the VCS server receives a call information event (outgoing DN, incoming DN) transmitted by a telephone exchange apparatus. However, since one of the visual clients is in the log-off status, the connection status between the extension terminals based on the received information is not registered in the call connection information table in the VCS server. Subsequently, if the logged off visual client performs a log-on operation, then at this timing of the log-on operation, the VCS server does not receive the call information event (outgoing DN, incoming DN). No information associating the two parties with each other is present in the call connection information table in the VCS server. Thus, no video communication is started even with the logon statuses of both visual clients associated with the extensions for the two-party call.
It is possible to pre-register all visual clients registered in VCS as listeners regardless of whether or not the visual clients associated with extension terminals are in the log-on status. However, with this method, when, for example, 500 visual clients are already registered in VCS, even if only 100 visual clients are in the log-on status, the 500 visual clients are always registered as listeners, always imposing a heavy system load on the VCS server. This makes the operation of the VCS server unstable.